Oh yes, good idea - and you can see if the input resistance of the meter affects the Arduino
reading. Good meters tend to be 10Mohm or more, cheap ones might be 1M. My
multimeter doesn't have its input resistance marked on it even, which is shocking
really.... The manual reveals 10M on all but 60mV and 600mV ranges
which are FET input direct (> 100M).
To explain a little about multimeters - to get the different ranges a network of resistive
dividers is used on the voltage inputs. Thus when you connect this to another resistive
divider network to measure voltage you are changing the network you are measuring.
You have to hope the resistances used in the multmeter are much larger than in the
circuit you measure...
So beware when measure voltages of high impedance circuits with a multimeter...